D.C. Mayor Marion Barry, citing the continuing decline in the city's school enrollment, proposed yesterday to slash next year's school operating budget by $10 million -- or 4 percent -- by closing schools and eliminating 839 jobs.

If it is approved by the City Council and Congress, the budget cut would be the first ever for the city's school system, despite decreasing enrollments in recent years.

Barry proposed a $237.1 million budget for fiscal 1981, which starts Oct. 1, 1980, down $10 million from the estimated figure for the fiscal 1980 budget and nearly $3 million less than for fiscal 1979.

Barry, who got his start in D.C. elective politics as president of the School Board, recently voiced concern that the city's younger black middle class is taking its children out of public schools because of what it sees as a lack of quality education there.

Yesterday Barry justified the proposed 1980-81 budget cut at a press conference, saying, "Everybody has to take their share of sacrifices. It's a tough time.

"I'm not convinced that money is the only answer to our school problems," the mayor said.

Barry said that under his $1.5 billion over-all city budget proposal, spending for the schools would be cut less than for some other city agencies, such as the Department of Human Resources.

The mayor said that D.C. school enrollment would decline from 113,858 in the last school year to about 101,500 next fall and that the school Board would have to make some "tough decisions" to close under-used schools and trim the schools' 9.655-person work force by about 9 per cent.

D.C. budget director Gladys W. Mack said she was not sure how many of the 839 job slots were now filled.

Mack said the decrease of 839 jobs partly corresponded to the decline in enrollment, but also included elemination of vacant, unfunded job positions.

The mayor did not specify the number of schools that should be closed or be possible candidates for closure.

Barry also called the School Board "really irresponsible" for not submitting a budget proposal to his aides.

School Board President Minnie S. Woodson said the board approved a $279 million spending plan in mid-August, although supporting documents for the budget may not have been forwarded to the mayor's office.

Woodson, who is retiring from the board Dec. 31, described Barry's budget proposal as "a very drastic situation for the school system."

She said that if the budget eventually is approved as proposed by Barry, various school functions possibly would have to be assumed by other city agencies, such as job counseling, adult education and school security.

She dismissed Barry's reliance on declining enrollments as his reason for cutting the school budget, saying, "The whole city's population is declining, but I don't see him cutting back police. You cut back on your educational system you're going to have more people in jail.

"I'm wondering what the goals and objectives of this city are," she said.

She said that if the 838 job slots are cut, the school system would have "to come to the bare minimum everywhere" and that some administrators would be among those losing their jobs.

She said that closing schools -- always an emotion-charged issue -- would result in minimal savings. She estimated that only $3 million could be saved by closing 10 schools.